In the manufacture of semiconductor integrated circuits, plasma etching is performed on a target substrate such as a semiconductor wafer. During the plasma etching, radicals and ions generated in the plasma may move toward and adhere to a bevel surface and a backside of a peripheral portion of a target substrate. Accordingly, a deposit layer referred to as Bevel/Backside Polymer (BSP) is annularly formed at the peripheral portion of the target substrate. The BSP may have a bad influence on the semiconductor integrated circuits and, thus, is required to be removed. Japanese Patent Application Publication No. 2009-123831 and its corresponding U.S. Patent Application Publication No. 2009-0143894 disclose a technique for removing BSP by heat treatment using laser and ozone gas.
In the above-disclosed technique, spotted laser light is irradiated on a target substrate. Accordingly, the laser light is made to irradiate onto the BSP circumferentially formed at a peripheral portion of a target substrate while varying a laser irradiation position on the target substrate by rotating the target substrate.
However, when laser irradiation is performed while varying a laser irradiation position on the target substrate by relatively moving the target substrate and the laser, it takes long time to perform a BSP removing process and a throughput of the BSP removing process is low. Alternatively, it may be possible to rotate the wafer W at a high speed by using a high output laser to increase the throughput. In such a case, however, it is difficult to improve a throughput because it takes time to increase and decrease the rotation speed of the wafer W and, further, particles may be generated due to disturbance in the atmosphere caused by high rotation. Further, when the laser light is irradiated to the target substrate rotated at a high speed by using a high output laser, rapid heating and cooling may occur at the laser irradiation position, and thus peeling of BSP is easily generated by heat stress, thereby causing contamination of the target substrate.